Question

The density of a 30% by mass solution of acetic acid in water is 1.250 g/mL. Its molarity is:

• A. 2.5 M
• B. 12.5 M
• C. 6.25 M
• D. 1.25 M

Answer 1

The correct option is C 6.25 M

Assuming 1000 mL of the solution.
Mass of the solution = $1.250\times 1000=1250g$
Mass of acetic acid = $1250\times \frac{30}{100}=375g$
Molar mass of acetic acid = 60 g
Thus, moles of acetic acid = $\frac{375}{60}$
Hence, the molarity of the solution,
= $\frac{\frac{375}{60}}{1}=6.25M$